SAND BAR DEVELOPMENT AFTER FLUSHING AT THE NATORI RIVER MOUTH

摘要

Morphology at the Natori River mouth in Japan often changes under the combinative actions of waves, currents and river flows. As a result, sand bar forms at the mouth frequently. In flood season, high river discharges contributing with strong wave from the Pacific Ocean cause sand bar at the mouth being breached and flushed. Sand bar on the left side of the Natori River mouth often be flushed in the flood with high water level and river discharge. However, after the flood, sand bar was recovered quickly by wave-induced sediment transport from the ocean. This study analyzes recovery process of sand bar after flushing at the Natori River mouth through observation data. There were four types of sand bar development from the beginning to fully recovery that were classified through the observation of sand bar evolution at the mouth after the floods in 1986, 1989 and 2002. The study also proposed the duration of recovery process of sand bar at the river mouth after flushing.